The risk of herpes zoster among patients with ankylosing spondylitis: A population-based cohort study in Taiwan

Objectives The incident rate of herpes zoster (HZ) is higher in some autoimmune diseases; however the relationship of HZ and ankylosing spondylitis (AS) is still unclear. This research aims to determine the incidence of HZ in Taiwan AS patients. Methods This study included 2819 AS patients and 11 276 non-AS controls between 2003 and 2013. All participants were selected from the Longitudinal Health Insurance Database 2000 Taiwan. The endpoint was diagnosis of HZ by International Classification of Diseases, Ninth Revision, Clinical Modification coding for at least 3 outpatient visits or one admission until the end of 2013. We used Chi-square test, Cox proportional hazard models and a Kaplan-Meier analysis to calculate the hazards ratio (HR), disease-free survival and incidental density of HZ. Subgroup analysis and sensitivity tests were also done. Results Comorbidities such as chronic urticaria, inflammatory bowel disease, thyroid disorders, hypertension, diabetes mellitus, hyperlipidemia, coronary artery disease, cerebrovascular accident, were higher in patients with AS than that in controls. Patients age >= 60 or comorbid disease such as thyroid disorders or cancer had a higher HR of HZ; the adjusted HRs were 2.273 (95% CI 1.314-3.931), 1.577 (95% CI 1.008-2.466) and 1.855 (95% CI 1.248-2.758) respectively, on multivariable modeling. The crude HR for HZ among AS patient was 1.178 (95% CI 0.953-1.455, P > 0.05), and the adjust HZ was 1.070 (95% CI 0.835-1.371, P > 0.05), compared to non-AS controls. Conclusions There is no difference in incidence rate of HZ between Taiwan AS patients and non-AS controls. Among AS patients, age and cancer were major risk factors for incidental HZ.